The present invention pertains generally to a radiation detecting and shielding device for reducing radiation exposure to healthy tissue of a patient undergoing radiation therapy, as well as detecting the amount of radiation delivered to the patient. More particularly, the invention pertains to protecting the contra-lateral breast or chest wall of a patient undergoing radiotherapy as well as sensing the amount of radiation on or near a patient""s skin on the non-treated side of the body.
Radiation therapy or radiotherapy for the chest wall or breast area of a patient has been utilized frequently for the treatment of localized cancer such as breast cancer. A patient typically undergoes a series of radiation treatments in which the treatment area is irradiated with a high energy radiation dose on the order of 25 to 75 Gray (Gy.) units, with a typical treatment dose in the range of 50 to 60 Gy. The most common radiation therapy technique for treating breast cancer utilizes opposing tangential radiation beams. A pair of wedges are often used in conjunction with this technique to obtain a more uniform treatment dose.
It is a growing concern among researchers that patients are exposed to scattered radiation in the adjacent region of the radiation field, particularly in the contralateral breast or chest wall in treatment of the breast or chest area. For patients undergoing breast cancer radiotherapy treatment, it has been estimated that the contra-lateral breast receives a scattered radiation dose between 5% to 13% of the prescribed treatment dose. Some patients may receive an even higher percentage of the dose depending on the patient""s anatomy and the treatment angles utilized. Further, for patients treated with a conventional dose of 50 Gray using traditional tangential fields, the dose to the contra-lateral breast has been estimated to be on the order of 2.5-6.0 Gray at a central axis corresponding to approximately 5 centimeters over the mid-line. Although the effects of this dose of scattered radiation are not yet well understood, one study has suggested that women under 45 years of age who had been treated for breast cancer by radiation therapy had an increased risk by a factor of 1.5 of contralateral breast cancer as compared to controls.
Radiotherapy to the breast region poses an increased exposure to scattered radiation dose compared to other sites of the body due to the wedge angles, beam accessories, and position of the linear accelerator gantry and collimator used for treatment. One source of scattered radiation is wedge scatter which results from the radiation beam scattered from the wedges used to shape the beam""s energy. A second source of scattered radiation is caused by the collimator head leakage and scattered radiation from the primary collimators. A third source of scattered radiation is due to the internal scattering of the treatment beam in various directions within the patient""s body.
It is generally considered prudent practice to reduce a patient""s exposure to unnecessary scattered radiation if it is reasonable to do so. Prior art shielding devices have generally been developed to protect patients against low energy radiation such as that generated by typical x-rays and the like. These prior art devices have generally comprised a thin flexible layer of shielding material such as lead, which is sandwiched between fabric and which is generally worn and supported by the patient. One major disadvantage to these type of devices is that they are not effective for shielding patients from high energy radiation which is typically used in breast cancer treatment and tumor reduction. Another disadvantage to this type of device is that the design of the shield is not conducive to alteration, i.e., increasing the lead thickness to protect against high energy radiation since the lead would be too heavy and cumbersome for a patient to support. Third, these prior art devices are not conducive to being positioned in close proximity to the treatment area without interfering with the treatment beams from the collimator. Thus, because of these difficulties, it is currently accepted practice for patients undergoing breast radiotherapy to forgo the use of shields which reduce radiation exposure to non-treatment areas.
Radiotherapy treatment techniques have also been modified in order to reduce the radiation dose to the contra-lateral breast. One prior art technique is to substitute a thicker lateral wedge in place of the medial wedge. While this technique may reduce scattered radiation exposure to the contra-lateral breast, it may result in an undesirable non-homogeneous dose across the treatment region.
It is thus highly desirable to have a new and improved method and apparatus for substantially reducing the scattered radiation dose to the non-treatments areas of the patient undergoing high energy external radiotherapy such as that utilized in treating localized breast cancer. It is further desired to have a shielding device which is self-supporting and is easily manipulated into position without interfering with the treatment beam. In addition, it is desired to have a device which senses the radiation adjacent a patient""s skin and whether the device is correctly positioned or is positioned in error too close to the treatment beam or target area. Thus, it is highly desirable to have an improved device and method which significantly reduces the prior art problems.
The present invention provides in one aspect a radiation shield for shielding a patient undergoing radiotherapy from scattered radiation, the shield comprising: a leading edge section having an inner surface complementary shaped to conform to a patient""s anatomy, and said shield being comprised of a radiation absorbing material for absorbing high energy radiation.
The present invention provides in another aspect a radiation shield and support stand assembly for shielding a patient undergoing radiotherapy, the device comprising a shield made of radiation absorbing material for absorbing high energy radiation and a support stand for supporting said shield.
The present invention provides in yet another aspect a radiation shielding device for shielding a patient undergoing radiotherapy, the device comprising: a shield made of radiation absorbing material for absorbing high energy radiation with said plate having an external layer of material for absorbing low energy electrons.
The present invention provides in still another aspect a radiation shield for shielding the contralateral breast of a patient, the shield comprising a leading edge section having an exterior surface shaped such that a distal edge of said shield may be placed in close proximity with the midplane of a patient with said exterior surface being parallel and located in close proximity to said radiotherapy beams.
These and other aspects of the invention are herein described in particularized detail with reference to the accompanying Figures.